Rotary encoders are frequently used for determining the angular position of two machine parts rotatable relative to each other. Often, such rotary encoders are employed as measuring devices for determining the absolute angular position over multiple revolutions (multiturn function) of corresponding drive shafts. In so doing, the rotary motion is recorded incrementally or absolutely. In connection with gear racks and gear wheels or with threaded spindles, linear motions can also be measured by an angular position encoder.
During normal operation, often the angular position is exactly determined by optical scanning of a graduated disk, while a magnetic scanning principle is used for counting the revolutions of the drive shaft. In general, it is desirable that the revolutions of corresponding drive shafts also are counted when the rotary encoder is not connected to an external voltage source, e.g., when the power supply is interrupted. To achieve this functionality with respect to an emergency operation, rotary encoders are frequently equipped with what are referred to as multiturn gear units. Multiturn gear units of this kind reduce the rotary motion of the drive shaft. For example, the position of a gear wheel in the multiturn gear unit may then be scanned using a magnetic measuring principle. The rotary motion of the corresponding gear wheel also takes place when the power supply of the rotary encoder is interrupted, e.g., when the drive shaft moves due to gravitational forces.
German Published Patent Application No. 10 2004 062 448 describes a rotary encoder in which a plurality of magnetic-pole segments are disposed over the periphery of a shaft. Upon leading the magnetic-pole segments past the free ends of flux concentrators, a sudden magnetic reversal of a ferromagnetic element takes place, thereby making sufficient electrical energy available for activating a memorizing counter.
Moreover, European Published Patent Application No. 0 724 712 describes an angle-of-rotation sensor by which an angular position can be determined in energy-autonomous manner utilizing a plurality of pulse wires and by the use of logic operations.
Such conventional rotary encoders have the disadvantage, for example, that they are only able to be produced with a comparative degree of complexity, and are costly to manufacture.